The Bay is approximately 200 miles (320 km) long from its northern headwaters in the Susquehanna River to its outlet in the Atlantic Ocean. It is 2.8 miles (4.5 km) wide at its narrowest (between Kent County's Plum Point near Newtown and the Harford County shore near Romney Creek) and 30 miles (48 km) at its widest (just south of the mouth of the Potomac River). Total shoreline including tributaries is 11,684 miles (18,804 km), circumnavigating a surface area of 4,479 square miles (11,601 km2). Average depth is 21 feet (6.4 m), reaching a maximum of 174 feet (53 m).[4] The Bay is spanned twice, in Maryland by the Chesapeake Bay Bridge from Sandy Point (near Annapolis) to Kent Island and in Virginia by the Chesapeake Bay Bridge-Tunnel connecting Virginia Beach to Cape Charles. Known for both its beauty and bounty, the Bay has become "emptier", with fewer crabs, oysters and watermen in past years.[5] Recent restoration efforts begun in the 1990s have been ongoing and show potential for growth of the native oyster population.[6][7] The health of the Chesapeake Bay improved in 2015, marking three years of gains over the past four years, according to a new report by the University of Maryland.[8]

Contents

The word Chesepiooc is an Algonquian word referring to a village "at a big river". It is the seventh oldest surviving English place-name in the United States, first applied as "Chesepiook" by explorers heading north from the Roanoke Colony into a Chesapeake tributary in 1585 or 1586. The name may also refer to the Chesepian or Chesapeake people, a Native American tribe who inhabited the area now known as South Hampton Roads in the U.S. state of Virginia. They occupied an area that is now the Norfolk, Portsmouth, Chesapeake, and Virginia Beach areas.[9] In 2005, Algonquian linguist Blair Rudes "helped to dispel one of the area's most widely held beliefs: that 'Chesapeake' means something like 'great shellfish bay.' It does not, Rudes said. The name might actually have meant something like 'great water,' or it might have just referred to a village location at the Bay's mouth."[10] In addition, the name is almost always prefixed by "the" in usage by local residents: "The Chesapeake", "The Chesapeake Bay" and "The Bay".[11]

The Chesapeake Bay is an estuary to the North Atlantic, lying between the Delmarva Peninsula to the east and the North American mainland to the west. It is the ria, or drowned valley, of the Susquehanna River, meaning that it was the alluvial plain where the river flowed when the sea level was lower. It is not a fjord, because the Laurentide Ice Sheet never reached as far south as the northernmost point on the Bay. North of Baltimore, the western shore borders the hilly Piedmont region of Maryland; south of the city the Bay lies within the state's low-lying coastal plain, with sedimentary cliffs to the west, and flat islands, winding creeks and marshes to the east. The large rivers entering the Bay from the west have broad mouths and are extensions of the main ria for miles up the course of each river.

The Bay's geology, its present form, and its very location were created by a bolideimpact event at the end of the Eocene (about 35.5 million years ago), forming the Chesapeake Bay impact crater and the Susquehanna River valley much later. The Bay was formed starting about 10,000 years ago when rising sea levels at the end of the last ice age flooded the Susquehanna River valley.[3] Parts of the Bay, especially the Calvert County, Maryland, coastline, are lined by cliffs composed of deposits from receding waters millions of years ago. These cliffs, generally known as Calvert Cliffs, are famous for their fossils, especially fossilized shark teeth, which are commonly found washed up on the beaches next to the cliffs. Scientists' Cliffs is a beach community in Calvert County named for the desire to create a retreat for scientists when the community was founded in 1935.[12]

Much of the Bay is shallow. At the point where the Susquehanna River flows into the Bay, the average depth is 30 feet (9 m), although this soon diminishes to an average of 10 feet (3 m) southeast of the city of Havre de Grace, Maryland, to about 35 feet (11 m) just north of Annapolis. On average, the depth of the Bay is 21 feet (6.4 m), including tributaries;[13] over 24 percent of the Bay is less than 6 ft (2 m) deep.[14]

Because the Bay is an estuary, it has fresh water, salt water and brackish water. Brackish water has three salinity zones: oligohaline, mesohaline, and polyhaline. The freshwater zone runs from the mouth of the Susquehanna River to north Baltimore. The oligohaline zone has very little salt. Salinity varies from 0.5 ppt (parts per thousand) to 10 ppt, and freshwater species can survive there. The north end of the oligohaline zone is north Baltimore and the south end is the Chesapeake Bay Bridge. The mesohaline zone has a medium amount of salt and runs from the Bay Bridge to the mouth of the Rappahannock River. Salinity there ranges from 10.7 ppt to 18 ppt. The polyhaline zone is the saltiest zone, and some of the water can be as salty as sea water. It runs from the mouth of the Rappahannock River to the mouth of the Bay. The salinity ranges from 18.7 ppt to 36 ppt. (36 ppt is as salty as the ocean.)[15]

The climate of the area surrounding the Bay is primarily humid subtropical, with hot, very humid summers and cold to mild winters. Only the area around the mouth of the Susquehanna River is continental in nature, and the mouth of the Susquehanna River and the Susquehanna flats often freeze in winter. It is rare for the surface of the Bay to freeze in winter, something that happened most recently in the winter of 1976–77.[16]

The largest rivers flowing directly into the Bay, from north to south, are:

Although the Bay is farther north than its typical habitat range, a male manatee visited the Bay several times between 1994 and 2011. The manatee, recognizable due to distinct markings on its body, was nicknamed "Chessie" after a legendary sea monster that was allegedly sighted in the Bay during the 20th century.[29][30][31] The same manatee has been spotted as far north as Rhode Island, and was the first manatee known to travel so far north.[32] Other manatees are occasionally seen in the Bay and its tributaries, which contain sea grasses that are part of the manatee's diet.[33]

The Chesapeake Bay is also home to a diverse flora, both land and aquatic. Common submerged aquatic vegetation includes eelgrass and widgeon grass. A report in 2011 suggested that information on underwater grasses would be released, because "submerged grasses provide food and habitat for a number of species, adding oxygen to the water and improving water clarity."[34] Other vegetation that makes its home in other parts of the Bay are wild rice, various trees like the red maple, loblolly pine and bald cypress, and spartina grass and phragmites.[35]Invasive plants have taken a significant foothold in the Bay; plants such as Brazilian waterweed, native to South America, have spread to most continents with the help of aquarium owners, who often dump the contents of their aquariums into nearby lakes and streams. It's highly invasive, and has the potential to flourish in the low-salinity tidal waters of the Chesapeake Bay. Dense stands of Brazilian waterweed can restrict water movement, trap sediment and affect water quality. Various local K-12 schools in the Maryland and Virginia region often have programs that cultivate native bay grasses and plant them in the Bay.

The Bay would again see conflict during War of 1812. During the year of 1813, from their base on Tangier Island, British naval forces under the command of Admiral George Cockburn raided and plundered several towns on the shores of the Chesapeake, treating the Bay as if it were a "British Lake". The Chesapeake Bay Flotilla, a fleet of shallow-draft armed barges under the command of U.S. Navy Commodore Joshua Barney, was assembled to stall British shore raids and attacks. After months of harassment by Barney, the British landed on the west side of the Patuxent at Benedict, Maryland, the Chesapeake Flotilla was scuttled, and the British trekked overland to burn the U.S. Capitol in August 1814. A few days later in a "pincer attack", they also sailed up the Potomac River to attack Fort Washington below the National Capital and demanded a ransom from the nearby port town of Alexandria, Virginia.

There were so-called "Oyster Wars" in the late 19th and early 20th centuries. Until the mid-20th century, oyster harvesting rivaled the crab industry among Chesapeake watermen, a dwindling breed whose skipjacks and other workboats were supplanted by recreational craft in the latter part of the century.[44]

During the later half of the 19th century and first half of the 20th century, the Bay was plied by passenger steamships and packet boat lines connecting the various cities on it, notably the Baltimore Steam Packet Company ("Old Bay Line").

Example Chesapeake Bay tides from Baltimore and the Chesapeake Bay Bridge Tunnel for quarter and full moons during June 2013.

Tides in the Chesapeake Bay exhibit an interesting and unique behavior due to the nature of the topography (both horizontal and vertical shape), wind driven circulation, and how the Bay interacts with oceanic tides. Research into the peculiar behavior of tides both at the northern and southern extents of the Bay began in the late 1970s. One study noted sea level fluctuations at periods of 5 days, driven by sea level changes at the Bay's mouth on the Atlantic coast and local lateral winds, and 2.5 days, caused by resonant oscillations driven by local longitudinal winds,[47] while another study later found that the geometry of the Bay permits for a resonant period of 1.46 days.[48]

At the Chesapeake Bay Bridge Tunnel (CBBT) site, which lies at the southernmost point of the Bay where it meets the Atlantic Ocean near Norfolk, Virginia, and the capes of Charles and Henry, there is a distinct semi-diurnal tide throughout the lunar month, with small amplitude modulations during spring (new/full moon) vs. neap (one/three quarter moon) tidal periods. The main forcing of the CBBT tides are typical, semi-diurnal ocean tides that the East Coast of the United States experiences.

Baltimore, in the northern portion of the Bay, experiences a noticeable modulation to form its mixed tidal nature during spring vs. neap tides. Spring tides, when the sun-earth-moon system forms a line, cause the largest tidal amplitudes during lunar monthly tidal variations. In contrast, neap tides, when the sun-earth-moon system forms a right angle, are muted, and in a semi-diurnal tidal system (such as that seen at the CBBT site) this can be seen as a lowest intertidal range.

Two interesting points that arise from comparing these two sites at opposite ends of the Bay are their tidal characteristics - semi-diurnal tide for CBBT and mixed tide for Baltimore (due to resonance in the Bay) - and the differences in amplitude (due to dissipation in the Bay).

The Bay is mostly known for its seafood production, especially blue crabs,[49]clams and oysters. In the middle of the 20th century, the Bay supported 9,000 full-time watermen, according to one account.[49] Today, the body of water is less productive than it used to be because of runoff from urban areas (mostly on the Western Shore) and farms (especially on the Eastern Shore and in the Susquehanna River watershed), over-harvesting, and invasion of foreign species.

The plentiful oyster harvests led to the development of the skipjack, the state boat of Maryland, which is the only remaining working boat type in the United States still under sail power. Other characteristic bay-area workboats include sail-powered boats such as the log canoe, the pungy, the bugeye, and the motorized Chesapeake Bay deadrise, the state boat of Virginia.[50]

In contrast to harvesting wild oysters, oyster farming is a growing industry for the Bay to help maintain the estuary's productivity as well as a natural effort for filtering impurities such as excess nutrients from the water in an effort to reduce the effects of man-made pollution. The Chesapeake Bay Program is using oysters to reduce the amount of nitrogen compounds entering the Chesapeake Bay.[51]

Oysters are hermaphroditic and will change gender at least once during their lifetime, often starting as male and ending as female; there are numerous ways to cook and eat them, as well as recipes and sauces to accompany oyster dishes.[44] One account:

The Chesapeake oyster – sometimes called Chesapeake white gold – has a flavor and texture that begs connoisseurs to come back and shuck just a few more.

The Bay is famous for its rockfish, a regional name for striped bass. Once on the verge of extinction, rockfish have made a significant comeback because of legislative action that put a moratorium on rockfishing, which allowed the species to re-populate. Rockfish can now be fished in strictly controlled and limited quantities.

The Chesapeake Bay is a main feature for tourists who visit Maryland and Virginia each year.[52] Fishing, crabbing, swimming, boating, kayaking,[18] and sailing are extremely popular activities enjoyed on the waters of the Chesapeake Bay. As a result, tourism has a notable impact on Maryland's economy.[53] One report suggested that Annapolis was an appealing spot for families, water sports and boating.[54] Commentator Terry Smith spoke about the Bay's beauty:

The water is glassy, smooth and gorgeous, his wake white against the deep blue. That's the problem with the Chesapeake. It's so damned beautiful.[42]

One account suggested how the Chesapeake attracts people:

You see them everywhere on Maryland's Eastern Shore, the weekend sailors. They are unmistakable with their deep tans, their baggy shorts, their frayed polo shirts, their Top-Siders worn without socks. Some may not even own their own boats, much less win regattas, but they are inexorably drawn to the Chesapeake Bay ... I planned to spend my days boating, eating as many Chesapeake Bay blue crabs as possible and making a little study of Eastern Shore locals. For city folk like me, they're interesting, even exotic –the weather-beaten crabbers and oystermen called "watermen," gentlemen-farmers and sharecroppers, boat builders, antiques dealers – all of whom sound like Southerners with mouthfuls of marbles when they talk. — Susan Spano, Los Angeles Times, 2008[55]

Environmental Protection Agency photo of dead menhaden floating in the bay in June 1973

Reeds along the bay

In the 1970s, the Chesapeake Bay was found to contain one of the planet's first identified marine dead zones, where waters were so depleted of oxygen that they were unable to support life, resulting in massive fish kills. Today the Bay's dead zones are estimated to kill 75,000 tons of bottom-dwelling clams and worms each year, weakening the base of the estuary's food chain and robbing the blue crab in particular of a primary food source. Crabs are sometimes observed to amass on shore to escape pockets of oxygen-poor water, a behavior known as a "crab jubilee". Hypoxia results in part from large algal blooms, which are nourished by the runoff of residential, farm and industrial waste throughout the watershed. One report in 2010 criticized Amish farmers for having cows that "generate heaps of manure that easily washes into streams and flows onward into the Chesapeake Bay".[56]

U.S. Navy sailors looking for trash during "Clean The Bay Day" in 2008

The runoff and pollution have many components that help contribute to the algal bloom, which is mainly fed by phosphorus and nitrogen.[57] This algae prevents sunlight from reaching the bottom of the Bay while alive and deoxygenates the Bay's water when it dies and rots. The erosion and runoff of sediment into the Bay, exacerbated by devegetation, construction and the prevalence of pavement in urban and suburban areas, also blocks vital sunlight. The resulting loss of aquatic vegetation has depleted the habitat for much of the Bay's animal life. Beds of eelgrass, the dominant variety in the southern Chesapeake Bay, have shrunk by more than half there since the early 1970s. Overharvesting, pollution, sedimentation and disease have turned much of the Bay's bottom into a muddy wasteland.[58]

One particularly harmful source of toxicity is Pfiesteria piscicida, which can affect both fish and humans. Pfiesteria caused a small regional panic in the late 1990s when a series of large blooms started killing large numbers of fish while giving swimmers mysterious rashes; nutrient runoff from chicken farms was blamed for the growth.[59]

The Bay improved slightly in terms of the overall health of its ecosystem, earning a rating of 31 out of 100 in 2010, up from 28 in 2008.[2] An estimate in 2006 from a "blue ribbon panel" said cleanup costs would be $15 billion.[42] Compounding the problem is that 100,000 new residents move to the area each year.[42] A report in 2008 in the Washington Post suggested that government administrators had overstated progress on cleanup efforts as a way to "preserve the flow of federal and state money to the project."[60] In January 2011, there were reports that millions of fish had died, but officials suggested it was probably the result of extremely cold weather.[61]

Oyster boats at war off the Maryland shore (1886 wood engraving). Regulation of the oyster beds in Virginia and Maryland has existed since the 19th century.

While the Bay's salinity is ideal for oysters and the oyster fishery was at one time the Bay's most commercially viable,[62] the population has in the last fifty years been devastated. Maryland once had roughly 200,000 acres (810 km2) of oyster reefs. Today it has about 36,000.[62] It has been estimated that in pre-colonial times, oysters could filter the entirety of the Bay in about 3.3 days; by 1988 this time had increased to 325 days.[63] The harvest's gross value decreased 88% from 1982 to 2007.[64] One report suggested the Bay had fewer oysters in 2008 than 25 years earlier.[5]

A cluster of oysters grown in a sanctuary

The primary problem is overharvesting. Lax government regulations allow anyone with a license to remove oysters from state-owned beds, and although limits are set, they are not strongly enforced.[62] The overharvesting of oysters has made it difficult for them to reproduce, which requires close proximity to one another. A second cause for the oyster depletion is that the drastic increase in human population caused a sharp increase in pollution flowing into the Bay.[62] The Bay's oyster industry has also suffered from two diseases: MSX and Dermo.[65]

The depletion of oysters has had a particularly harmful effect on the quality of the Bay. Oysters serve as natural water filters, and their decline has further reduced the water quality of the Bay. Water that was once clear for meters is now so turbid that a wader may lose sight of his feet while his knees are still dry.

Efforts of federal, state and local governments, working in partnership through the Chesapeake Bay Program, and the Chesapeake Bay Foundation and other nonprofit environmental groups, to restore or at least maintain the current water quality have had mixed results. One particular obstacle to cleaning up the Bay is that much of the polluting substances arise far upstream in tributaries lying within states far removed from the Bay. Despite the state of Maryland spending over $100 million to restore the Bay, conditions have continued to grow worse. Twenty years ago, the Bay supported over six thousand oystermen. There are now fewer than 500.[66]

Efforts to repopulate the Bay via hatcheries have been carried out by a group called the Oyster Recovery Partnership, with some success. They recently placed 6 million oysters on eight acres (32,000 m2) of the Trent Hall sanctuary.[67] Scientists from the Virginia Institute of Marine Science at the College of William & Mary claim that experimental reefs created in 2004 now house 180 million native oysters, Crassostrea virginica, which is far fewer than the billions that once existed.[68]

Singer and songwriter Tom Wisner recorded several albums, often about the Chesapeake Bay. The Boston Globe wrote that Wisner "always tried to capture the voice of the water and the sky, of the rocks and the trees, of the fish and the birds, of the gods of nature he believed still watched over it all."[73] He was known as the Bard of the Chesapeake Bay.[73]

The 1976 hit "Moonlight Feels Right" by Starbuck refers to Chesapeake Bay: "I'll take you on a trip beside the ocean / And drop the top at Chesapeake Bay."

^Also shown as "Chisupioc" (by John Smith) and "Chisapeack", in Algonquian "che" means "big" or "great", "sepi" means river, and the "oc" or "ok" ending indicated something (a village, in this case) "at" that feature. "Sepi" is also found in another placename of Algonquian origin, Mississippi. The name was soon transferred by the English from the big river and the village at that site to the entire bay. Stewart, George (1945). Names on the Land: A Historical Account of Place-Naming in the United States. New York: Random House. p. 23.